反应详情

Step 1 A solution of 3-bromo-2-methylaniline (0.662 mL, 5.37 mmol) and racemic 2-(benzyloxycarbonylamino)-4-(methylthio)butanoic acid (1.523 g, 5.37 mmol) in acetonitrile (25 mL) was treated with 1-hydroxy-7-azabenzotriazole (0.878 g, 6.45 mmol), diisopropylethylamine (1.877 mL, 10.75 mmol) and EDC (1.236 g, 6.45 mmol) and stirred at rt. After 20.5 h, the mixture was diluted with water and ethyl acetate. The organic phase was separated, washed with 1 M aqueous HCl and NaHCO3 (aq) and filtered to remove a flocculent white solid. The filtrate was dried and concentrated, and the residue was recrystallized from ethanol to give racemic benzyl 1-(3-bromo-2-methylphenylamino)-4-(methylthio)-1-oxobutan-2-ylcarbamate as a tan solid (1.33 g, 69%). 1H NMR (400 MHz, chloroform-d) δ 8.08 (1H, br. s.), 7.68 (1H, d, J=7.9 Hz), 7.39 (1H, d, J=7.9 Hz), 7.34 (5H, s), 7.04 (1H, t, J=8.0 Hz), 5.58 (1H, d, J=7.9 Hz), 5.14 (2H, s), 4.53 (1H, q, J=7.0 Hz), 2.55-2.72 (2H, m), 2.28 (3H, br. s.), 2.17-2.27 (1H, m), 2.12 (3H, s), 2.01-2.10 (1H, m). Mass spectrum m/z 451, 453 (M+H)+.

1. customThe organic phase was separated
2. washwashed with 1 M aqueous HCl and NaHCO3 (aq)
3. filtrationfiltered
4. customto remove a flocculent white solid
5. customThe filtrate was dried
6. concentrationconcentrated
7. customthe residue was recrystallized from ethanol